Add back temporary experimental_ aliases for Server Actions APIs (#27461)

This adds back the `experimental_`-prefixed Server Actions APIs to the
experimental builds only, so that apps that use those don't immediately
break when upgrading. The APIs will log a warning to encourage people to
move to the unprefixed version, or to switch to the canary release
channel.

We can remove these in a few weeks after we've given people a chance to
upgrade.

This does not affect the canary builds at all, since they never had the
prefixed versions to begin with.

packages/react-dom/index.experimental.js

@@ -30,3 +30,30 @@ export {
   preinitModule,
   version,
 } from './src/client/ReactDOM';
+
+import type {FormStatus} from 'react-dom-bindings/src/shared/ReactDOMFormActions';
+import {useFormStatus, useFormState} from './src/client/ReactDOM';
+
+export function experimental_useFormStatus(): FormStatus {
+  if (__DEV__) {
+    console.error(
+      'useFormStatus is now in canary. Remove the experimental_ prefix. ' +
+        'The prefixed alias will be removed in an upcoming release.',
+    );
+  }
+  return useFormStatus();
+}
+
+export function experimental_useFormState<S, P>(
+  action: (S, P) => Promise<S>,
+  initialState: S,
+  permalink?: string,
+): [S, (P) => void] {
+  if (__DEV__) {
+    console.error(
+      'useFormState is now in canary. Remove the experimental_ prefix. ' +
+        'The prefixed alias will be removed in an upcoming release.',
+    );
+  }
+  return useFormState(action, initialState, permalink);
+}

packages/react/index.experimental.js

@@ -58,3 +58,18 @@ export {
   useTransition,
   version,
 } from './src/React';
+
+import {useOptimistic} from './src/React';
+
+export function experimental_useOptimistic<S, A>(
+  passthrough: S,
+  reducer: ?(S, A) => S,
+): [S, (A) => void] {
+  if (__DEV__) {
+    console.error(
+      'useOptimistic is now in canary. Remove the experimental_ prefix. ' +
+        'The prefixed alias will be removed in an upcoming release.',
+    );
+  }
+  return useOptimistic(passthrough, reducer);
+}